There are different types of online sim cards, and they come with different features. Some support full functionality (calls + sms + data), others are data/sms only, and some have limited voice roaming.
First thing I’d do is check with your provider and clarify the exact details of your plan, especially voice roaming support in the USA
For example, in catalogs like
sms-activate you can see that different providers offer different options: some include calls, some only SMS reception, etc. So it really depends on how your sim is configured.